Recently, pants-type disposable diapers have been widely used. Generally, the disposable diaper comprises a liquid permeable top sheet which locates at a side of a wearer, a liquid impermeable back sheet which locates at an opposite side of the wearer, and an absorbent body which is arranged between both these sheets at each center of a body peripheral region and a leg peripheral portion, such that double-faced adhesive tapes annexed to both end portions in the width direction of the body peripheral region in the back side are joined to the body peripheral region in the front side.
As shown in FIG. 39, a large number of body peripheral region elastic members 4F and 4B, and leg peripheral portion elastic members 5F and 5B (e.g., rubber threads, elastic film, or the like.) which extend in the width direction are arranged in the body peripheral region A10 and the leg peripheral portion 2 to be worn in a state where the body peripheral region A10 and the leg peripheral portion 2 certainly fit to a body trunk and hip of the wearer by the body peripheral region elastic members 4F and 4B, and leg peripheral portion elastic members 5F and 5B.
For the elastic member in this case, especially for the body periphery, typically rubber threads are used. The rubber threads are arranged throughout the circumference of a region unevenly distributed on a side of a waist opening edge of the body peripheral region (i.e., a region of a length range from the waist opening edge to a leg opening start end). It is general that an arrangement interval is 10 mm or more. Typically, the arrangement interval at the waist opening portion is made small, and to prevent excessive press at a ventral portion, the arrangement interval at an under waist portion (a portion at an under crotch side from the waist opening portion) is made large.
However, in the case of the above conventional disposable diaper, since the body peripheral region elastic members 4F and 4B and the leg peripheral portion elastic members 5F and 5B are also arranged on a portion corresponding to the absorbent body 3, the absorbent body 3 contracts as shown by arrows G1 and G2 due to elasticity of the body peripheral region elastic members 4F and 4B and the leg peripheral portion elastic members 5F and 5B. Then, a portion on which the body peripheral region elastic members 4F and 4B are arranged and an approximately center in a longitudinal direction which is a portion where body fluid stays in the absorbent body 3 particularly by expansion and contraction of the leg peripheral portion elastic members 5F and 5B contract to cause wrinkles. Thus, there has been a drawback that fitness between the absorbent body 3 and the hip portion is impaired and liquid leakage easily occurs.
In the conventional disposal diaper, an interval of three-dimensional gathers provided to protrude at the side of the wearer in both outer side edges of the absorbent body 3 becomes small due to contraction of the absorbent body 3, the three-dimensional gathers make inroads into a crotch portion when worn with displacement from side to side, and that has been a cause of leakage.
Thus, the pants-type disposable diaper where occurrence of clumsy wrinkles is prevented by providing a region having no elastic member in the body peripheral region is proposed. However, although this kind of pants-type disposable diaper make a good show, it have been difficult to be worn or to wear, and has slipped off in some cases. There has been a problem that the desired fitness feeling is not obtained.
Disposable wearing articles such as the above disposable diapers, disposable pants or the like are required to make a waist periphery, leg peripheries and a body periphery elasticizable to improve adhesiveness to the wearer. In this case, it can be also thought to utilize woven fabrics (stretch fabrics) where materials per se have elasticity, however, cost is too high to use it for disposal articles. Therefore, typically, a filamentous or obi-like elastic member is glued in a stretched state on a non-elastic sheet such as a non-woven fabric, a plastic film or the like to make the non-elastic sheet elasticizable.
To continuously manufacture such elastic sheet, a method is employed where while the non-elastic sheet is turned out from a roller and run, an elastic member is withdrawn from a roller and attached on the non-elastic sheet in a stretched state with a predetermined tension. However, there are some cases where a portion with no need of elasticity (hereinafter, non-elastic portion) and an elastic portion should be provided intermittently in a scanning direction of the sheet in terms of forms of disposable wearing articles or as a matter of convenience of cutting into individual products.
Although it is also thought for the non-elastic portion that the elastic portion is attached on the sheet without giving the tension, it is difficult in terms of manufacturing to promptly switch the stretched state with the tension to or from the state without the tension.
Therefore, typically, the non-elastic portion is provided by intermittently coating an adhesive on the sheet to provide an adhesive-applying portion and a non-applying portion alternately along the sheet scanning direction on the sheet, and cutting the elastic member present on the adhesive non-applying portion. Since the elastic member is not attached to the sheet on the adhesive non-applying portion, the elastic member cut at one site is stretched to the elastic member attached on the sheet to be relaxed, and stay there.
The method to cut the elastic member includes, for example, as the method described in Japanese Patent Laid-open Application No. 2000-26015, a method where the elastic member is cut by passing the sheet on which the elastic member is positioned between a first roller having a continuous linear convex portions (single-edged blade) continuing along a roller width direction and a second roller opposed thereto, and pressing or heating with the linear convex portions of the first roller.
However, in this conventional method, since cutting force is acted continuously and linearly along the roller width direction, the sheet portion where no elastic member exist is cut in some cases. Even when it is not cut, since the sheet such as non-woven fabric or the like becomes a thin film by heating and pressing, one sealing line with hard tactile remains across the portion where no elastic member exist. Thus, there has been a problem that both looks and wearing feeling become insufficient when made into products.
Thus, the present applicant has proposed a method for manufacturing elastic sheet wherein a laminate is made by positioning a single or a plurality of elastic members of filamentous, netty, sheet like or the like on a sheet or between upper and lower sheets in an extended state, the laminate is passed between a first roller wherein multiple convex portions are disposed on the surface and a second roller opposed to the first roller, and the elastic member of the laminate is cut by either one of pressing or heating between the convex portions of the first roller and the second roller.
According to such a method for manufacturing the elastic sheet, there are advantages obtained that there is no breaking of the sheet portion, wearing feeling becomes good because no linear hard sealing line remains or the like. However, due to a subsequent design change, necessity to partially regulate contractile force occurred in order to make a disposal wearing article further fit to a body shape as well as loosen constriction of the leg peripheries. As techniques for it, as shown in FIG. 40, the method where the elastic member is cut using a first roller wherein the convex portions are disposed in a region of a head-cutting home base shape in a constant pattern, i.e., using the first roller wherein a convex portion forming region is formed to have a region where a cutting length of the elastic member is gradually expanded, and the method where tensile force is modulated by modulating extensible force of each elastic member with making a cut location rectangular as being conventional, are studied, respectively. However, in the former case, it was found that staving and slivering of substrates occur in the range of signs Q1 and Q2 shown in the same figure only by changing the formation range of the convex portions. On the other hand, in the latter case, although it becomes possible to partially change the extensible force without causing staving and slivering of the sheet, it was difficult to apply for an actual manufacturing line because an extensive equipment change is accompanied.
The object of the present invention is to provide a disposable diaper which improves fitness to a wearer as well as certainly prevents leakage of body fluid, makes a fine showing, is easy to be worn and wear, and causes no slip off.
Another object of the present invention is to provide a method for manufacturing an elastic sheet used for disposable diapers, wherein cut of an elastic member without possibility of sheet breakage is made possible as well as a cutting location of the elastic member can be optionally changed without causing staving and slivering, and a disposable diaper using the elastic sheet.